The invention relates to a method for the measurement of the relative speed of an object according to patent claim 1.
Methods for the determination of object separations or spacing distances are increasingly utilized in obstacle warning systems for motor vehicles, in order to warn the drivers of the motor vehicles of sources of danger on the roadway. For example, a method for the obstacle recognition is known from the DE 41 15 747 C2, in which an observation or monitoring space in front of a vehicle is repeatedly sensed or sampled with a laser source, in order to calculate the object separation or spacing distance from the signal transit time of the light emitted from the laser source and reflected on an object, and to warn the driver, through acoustic or optical signals, of a possible collision with the object, depending on the determined object separation.
It would be sensible or suitable in the estimation of the collision probability, to determine also the speed of the objects approaching the vehicle. While this could be determined through a differentiation of the time course or progression of the object separation, the result, however, would be inexact due to the noise increased or amplified through the differentiation. While the signal-to-noise ratio of the measurement result could be suppressed through a filtering, the filtering would, however, lead to an undesired time delay in the providing of the measurement result. Furthermore, it would be conceivable to improve the signal-to-noise ratio through increasing of the radiation power of the laser source, but an increasing of the radiation power is not desired, because this could lead to an eye injury of persons or animals that might look in the direction of the laser source.
Therefore, it is an underlying object of the invention to present a method for the determination of the relative speed of an object, that can be carried out with a low effort or expense, and provides exact measurement results.